An electrophotographic photoreceptor essentially comprises a charge generation layer (CGL) and charge transport layer (CTL) coated on a suitable substrate. The substrate may be an aluminized MYLAR polyester or an anodized aluminum drum (termed a PC drum). An aluminum drum can be coated with a suitable sub-layer and/or a barrier layer, derived by dispersing metal oxides in a polymer binder.
The charge generation layer comprises pigments or dyes selected from phthalocyanines, squaraines, azo compounds, perylenes etc. The pigment or dye may be dispersed or dissolved in a suitable solvent, with or without a polymer binder. The use of polymer binder helps improve the dispersion stability and improve the adhesion of the CGL to the core or other substrate. However, depending on the type of polymer binder being used, the sensitivity of the photoreceptor may be affected.
As printers are expected to perform at speeds of 30–50 pages-per-minute, it becomes imperative that the photoconductor charge and discharge at very short time intervals. The time frames required for 35 ppm, for example could relate to an expose-to-develop time in the order of 40–80 ms. Hence, there is a growing need to identify systems that improve the electrophotographic properties without compromising on other properties such as adhesion, fatigue, and the like.
Also, with a move towards faster systems, the drive towards lower cost becomes more demanding. One area where cost can be lowered is by using a cartridge that does not have a shutter for the photoconductor drum. Optionally, a separation of function can be envisioned wherein the photoconductor may be a part of the printer and not the toner cartridge. In this case, the photoconductor may be highly susceptible to exposure to room light, when the toner cartridge is replaced. Most photoconductor formulations are sensitive to the effect of room light (eg. fluorescent light).
As shown in this invention, the exposure to room light (fluorescent light) can cause severe fatigue (electrical and the related print) in the PC drum. This results in a print defect pattern. This invention addresses possible methods of mitigating any fatigue or deterioration in electrophotographic properties brought about by exposure to room light.
The acetosol yellow 5GLS of this invention is also known by the trademark SAVINYL YELLOW and as Colour Index Solvent Yellow 138. It is an ingredient of a more-than-twenty-year-old patent, specifically U.S. Pat. No. 4,362,798 to Anderson et al.
The foregoing U.S. Pat. No. 4,362,798 and U.S. Pat. No. 6,544,702 to Haggquist et al. disclose the use of acetosol yellow 5GLS as a room light fatigue mitigant, in a hydrazone transport. U.S. Pat. No. 5,545,499 (Balthis et al., Lexmark International, Inc.) discloses hydrazone charge transport.
JP 06-161123 A, published Jun. 7, 1994, (Mita Ind Co.) claims the use of cyclopentadienone type compound in the sensitive layer.
JP 64-040835 A, published Feb. 13, 1989 (Toshiba Corp.) describes the use of a tetraphenylcyclopentadienone in a N-ethylcarbazole hydrazone transport layer coated on a charge generating layer comprising of a tau-type phthalocyanine and polyvinylbutyral. In addition, a suitably substituted cyclohexenedienone is also disclosed.